The invention generally relates to the treatment of bone conditions in humans and other animals.
Injection devices similar to a household caulking gun are used to inject bone cement into bone. A typical bone cement injection device has a pistol-shaped body, which supports a cartridge containing bone cement. A trigger actuates a spring-loaded ram, which forces a volume of bone cement in a viscous condition through a suitable nozzle and into the interior of a bone targeted for treatment. According to the teachings of U.S. Pat. Nos. 4,969,888 and 5,108,404, a cavity can be first formed by compacting cancellous bone inside the bone, into which the bone cement is injected. Conventional cement injection devices provide no opportunity to override the spring action and quickly terminate the flow of cement, should the cavity fill before the spring-actuated load cycle is completed. Furthermore, once the spring-actuated mechanism is triggered, conventional cement injection devices do not permit the injection volume or inject rate to be adjusted or controlled in real time, in reaction to cancellous bone volume and density conditions encountered inside bone.
In a clinical procedure called vertebroplasty, bone cement is injected at high pressure (typically, about 700 psi) into the interior of a vertebral body, without the prior formation of a cavity. Because high pressure is used, there is little opportunity to quickly and accurately adjust cement flow in reaction to bone volume and density conditions encountered. Momentum generated by high pressure-induced cement flow continues to propel cement into the targeted bone site even after termination of the high pressure.
As a result of the relatively high pressure that conventional procedures rely upon, coupled with the effective lack of a short response time, the targeted bone interior can suddenly overfill. Excess filling material can be forced outside the bone interior, and into adjoining tissue regions, where the presence of filling material is not required or desired.
For these and other reasons, there is a need for new systems and methods for placing material into bones, with greater rate and volume control, a faster response time, and without requiring the use of high pressure.
The invention provides instruments, systems, and methods, which, in use, enable greater control over the placement of materials into bone.
One aspect of the invention provides an instrument for tamping material into bone through a subcutaneous path. The instrument comprises a body having a length and a terminus. The body includes markings located along the length at increments from the terminus. The markings allow the physician to gauge the position of the instrument in the subcutaneous path, as material is being tamped into bone. In particular, the markers allow the physician to tell at a glance the location of the terminus, in terms of how far beyond or short of the end of the subcutaneous path it is.
In one embodiment, the instrument is used by deploying a cannula to establish a subcutaneous path into bone. A material is introduced into bone through the cannula. The terminus of the instrument is advanced through the cannula to urge material residing in the cannula into bone.
Another aspect of the invention provides an apparatus for introducing material into bone through a subcutaneous cannula. The apparatus includes a delivery device to convey the material at a low delivery pressure. As used herein, a xe2x80x9clow delivery pressurexe2x80x9d is equivalent to the pressure at which liquid is expressed from 1 cc syringe by the application of moderate force to the syringe piston, which amounts to a pressure that is no greater than about 360 psi.
According to this aspect of the invention, the apparatus also includes a nozzle instrument capable of advancement through the subcutaneous cannula into bone. The nozzle comprises a proximal fitting to couple the nozzle instrument to the delivery device. The nozzle further comprises a nozzle terminus through which the material conveyed by the delivery device enters bone at the delivery pressure.
In one embodiment, the delivery device comprises a syringe.
In one embodiment, the apparatus further includes a tamping instrument, which is capable of advancement through the subcutaneous cannula. The tamping instrument has a tamping terminus which, during the advancement, urges material residing in the subcutaneous cannula into bone.
In one embodiment, the tamping instrument includes markings to visually gauge the advancement of the tamping terminus through the subcutaneous cannula.
In one embodiment, the apparatus is used by deploying a cannula to establish a subcutaneous path into bone. The delivery device is actuated to convey material at the delivery pressure through the nozzle terminus into bone.
Another aspect of the invention provides a tool for deployment into bone. The tool comprises a catheter tube having a distal region and an expandable structure carried by the distal region for compacting cancellous bone. The tool also includes an introducer sleeve slidably carried by the catheter tube for movement between a retracted position spaced from the expandable structure and an advanced position overlying the expandable structure. The introducer sleeve includes a tubular main body dimensioned to compress the expandable structure when the introducer sleeve is in the advanced position. A collar extends beyond the distal region of the catheter tube when the introducer sleeve is in the advanced position. The collar is dimensioned larger than the tubular main body to releasably engage an end of a cannula. Thus, the introducer sleeve both sizes and aligns the expandable structure for passage into the cannula through the end of the cannula.
Another aspect of the invention provides apparatus for introducing material into bone through a subcutaneous cannula. The apparatus includes a delivery device to convey the material at a low delivery pressure, i.e., a pressure no greater than about 360 psi. The apparatus also includes a nozzle instrument capable of advancement through the subcutaneous cannula into bone and comprising a proximal fitting to couple the nozzle instrument to the delivery device. The nozzle also includes a nozzle bore, through which the material conveyed by the delivery device enters bone at the delivery pressure. The apparatus further includes a stylet capable of advancement into the nozzle bore through the proximal fitting to close the nozzle bore and, with the nozzle instrument. Together, the nozzle and the stylet form a tamping instrument capable of advancement through the subcutaneous cannula to urge residual material from the subcutaneous cannula.
Another aspect of the invention provides a method for delivering material into bone. The method deploys a cannula through soft tissue to establish a subcutaneous path into bone. The method introduces a material into bone through the cannula. The method advances a tamping instrument through the cannula to urge material residing in the cannula into bone.
In one embodiment, the method delivers material at a low delivery pressure, i.e., a pressure no greater than about 360 psi.
In one embodiment, the introducing step uses a manual syringe.
The material can comprise medication or a material that sets to a hardened condition e.g., bone cement, or autograft tissue, or allograft tissue, or synthetic bone substitute, or combinations thereof.
In one embodiment, the method further includes the step of deploying a cavity forming instrument through the cannula to compress cancellous bone and form a cavity. In this embodiment, the introducing and advancing steps convey material into the cavity.